Heart disease is a major problem in society, and claims many lives per year. After a heart attack, only a small number of patients can be treated successfully and non-invasively using medicines, such as pharmaceuticals. However, with sufficient mechanical assistance to the heart function, a majority of patients may recover from a heart attack, including even those with cardiogenic shock.
In a conventional approach, a blood pump having a fixed cross-section is surgically inserted within the left ventricle of the heart and the aortic arch to assist the heart in its function. Surgical placement is required, since it is presently impractical or impossible to insert a pump of the size needed for sustaining adequate blood flow percutaneously. The object of the surgically inserted pump is to reduce the load on the heart muscle for a period of time, which may be as long as a week, allowing the affected heart muscle to recover while healing in a resting mode.
Surgical insertion, however, can cause additional serious stresses in heart failure cases. Percutaneous insertion of a left ventricular assist device (“LVAD”) therefore is desired. However, the conventional fixed cross-sectional diameter of such an LVAD cannot fit through the femoral artery of the leg in which it must travel to be positioned into the left ventricle. The maximum diameter of such a fixed diameter LVAD would have to be limited to approximately four millimeters for practical percutaneous insertion. This would limit the maximum pumped blood flow rate to approximately two liters per minute, approximately one-half the desired sustaining blood flow value for many cases. While the pumping rate can be increased by increasing the diameter of the device, particularly the diameter of the impeller, the size of the femoral artery is a limiting factor for percutaneous insertion. Hence, there is an urgent need for a pumping device that can be implanted through percutaneous insertion and yet provide the sustaining blood flow rates that conventional surgically implanted pumps provide.